1. Field of the Invention
The present invention relates to an internal combustion engine provided with a cooling pump that can be mechanically disconnected.
2. Description of the Related Art
Modern internal combustion engines nearly always comprise a liquid cooling system in which a circulation pump circulates coolant (typically water mixed with an antifreeze substance) along a cooling path which extends in part within the internal combustion engine to remove the heat in excess and in part within a radiator to surrender the heat in excess coming from the internal combustion engine into the external environment.
In most vehicles, the circulation pump is directly fed so as to be rotated by the crankshaft by the interposition of a mechanical belt or chain transmission (more rarely by means of gears).
When the internal combustion engine is started after a long stop (i.e. one sufficiently long to take the temperature of the internal combustion engine to ambient temperature levels), it would be appropriate not to cool the internal combustion engine in order to promote a rapid reaching of the optimal working temperature; indeed, only when the internal combustion engine is at the optimal working temperature can the maximum energy efficiency and the minimum generation of polluting substances (i.e. maximum ecological efficiency) be achieved. For this purpose, modern internal combustion engines are normally provided with a thermostat valve which bypasses the part of the cooling system dedicated to dispersing the heat into the environment (i.e. the radiator) so that the coolant does not surrender heat into the external environment until the coolant itself reaches a sufficiently high temperature (i.e. reaches the optimal working temperature).
However, when the internal combustion engine is cold (i.e. colder than the optimal working temperature), the circulation pump of the cooling system continues to work by unnecessarily drawing mechanical power from the crankshaft (and thus dissipating mechanical energy). Furthermore, the coolant circulation, although bypassing the radiator, in all cases causes a (minimum, yet not null) cooling of the internal combustion engine, which thus warms up slower than potentially possible.
In order to solve such a drawback, it has been suggested to use a circulation pump of the cooling system controlled by a dedicated electric motor, and thus entirely independent from the crankshaft in mechanical terms; in this manner, the electrically operated circulation pump may be operated only when necessary. However, particularly in high performance internal combustion engines, the circulation pump may require considerable power (particularly when the external temperature is hot and high power delivery is required, like when driving on a race track in summer) which would require the installation of a very high performance (and thus heavy and large) electric motor to activate the circulation pump and of a very high performance (and thus heavy and large) electric generator to generate the electricity needed to activate the circulation pump.
U.S. Pat. No. 1,665,765 and Japanese Patent Application No. 2003027942 describe an internal combustion engine having: a cooling system provided with a circulation pump, an auxiliary shaft which transmits the rotation movement to a circulation pump shaft, a mechanical transmission which transmits the rotation movement of the crankshaft to the auxiliary shaft, and a coupling device which is interposed between the circulation pump and the auxiliary shaft and is suited to mechanically connect/disconnect the pump shaft to/from the auxiliary shaft. However, such constructive solutions suggested in U.S. Pat. No. 1,665,765 and Japanese Patent Application No. 2003027942 cause an increase of the overall weight and dimensions of the internal combustion engine.